HttpClient方式实现RPC远程调用

问题：

RPC，所谓远程调用，就是由服务消费者发起请求调用服务提供者中的方法完成功能处理，然后服务提供者再将执行结果响应给服务消费者的一个过程。那么浏览器和服务器的交互方式，好像就是远程调用，那么我们能不能参照
浏览器和服务器交互的模式来实现项目之间的远程调用呢？

方案：

• 服务器消费者--->浏览器--->在服务消费者中声明类似浏览器发起请求和接收响应的代码。
• 服务器提供者--->MVC的web项目

实现：

HttpClient

使用：

1、服务提供者的代码就是正常的Web项目
2、服务器消费中导入HttpClient的jar包，然后编写相关代码完成rpc远程调用,参照源码

一.服务提供方代码

package com.bjsxt.controller;

import java.util.List;

import javax.annotation.Resource;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;

import com.alibaba.fastjson.JSON;
import com.bjsxt.pojo.Pet;
import com.bjsxt.service.PetService;

@Controller
public class PetCon {
    @Resource
    private PetService petServiceImpl;
    
    /**
     * 获取所有的宠物信息
     */
    @RequestMapping("pet")
    public String getPet(HttpServletRequest req){
        List<Pet> pl = petServiceImpl.getPetInfoService();
        req.setAttribute("pl", pl);
        return "pet.jsp";   
    }
    /**
     * 获取所有的宠物信息
     * @param pname
     * @param color
     * @return
     */
    @ResponseBody
    @RequestMapping("pet2")
    public List<Pet> getPet(String pname,String color){
        System.out.println("Pet2请求数据===="+pname+":"+color);
        List<Pet> pl = petServiceImpl.getPetInfoService();
        return pl;
        
    }
    
    /**
     * 处理Ajax请求，返回所有的宠物信息，Jsop方式
     * @param pname
     * @param color
     * @return 
     * callback({name:zhansgan,age:18})
     */
    @ResponseBody
    @RequestMapping(value="petAjax",produces="text/script;charset=UTF-8")
    public String getPetAjax(String callback,String pname,String color){
        System.out.println("getPetAjax请求数据==跨域=="+pname+":"+color);
        List<Pet> pl = petServiceImpl.getPetInfoService();
        //将数据转换为json字符串
        String jsonString = JSON.toJSONString(pl);
        return callback+"("+jsonString+")";
    }
    /**
     * 获取所有的宠物信息，coresFilter方式
     */
    @ResponseBody
    @RequestMapping("petFilter")
    public List<Pet> getPetFilter(String pname,String color){
        System.out.println("Pet2请求数据===="+pname+":"+color);
        List<Pet> pl = petServiceImpl.getPetInfoService();
        return pl;
        
    }
        
}

service接口和service实现类略....

pom.xml文件如下..

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.bjsxt.rpc</groupId>
  <artifactId>04-HttpServer</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <packaging>war</packaging>
   <properties>
    <commons.version>1.2</commons.version>
    <jsp.version>2.0</jsp.version>
    <jstl.version>1.2</jstl.version>
    <servlet.version>2.5</servlet.version>
    <spring.version>4.3.18.RELEASE</spring.version>
  </properties>
  <dependencies>
    <dependency>
      <groupId>commons-logging</groupId>
      <artifactId>commons-logging</artifactId>
      <version>${commons.version}</version>
    </dependency>
    
    <dependency>
        <groupId>javax.servlet</groupId>
        <artifactId>jsp-api</artifactId>
        <version>${jsp.version}</version>
        <scope>provided</scope>
    </dependency>
    <!-- servlet -->
    <dependency>
        <groupId>javax.servlet</groupId>
          <artifactId>servlet-api</artifactId>
          <version>${servlet.version}</version>
          <scope>provided</scope>
    </dependency>
    <!-- jstl -->
    <dependency>
        <groupId>javax.servlet</groupId>
        <artifactId>jstl</artifactId>
        <version>${jstl.version}</version>
    </dependency>
    
    <dependency>
         <groupId>org.springframework</groupId>
         <artifactId>spring-webmvc</artifactId>
         <version>${spring.version}</version>
    </dependency>
    <dependency>
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-databind</artifactId>
        <version>2.9.0</version>
    </dependency>
    <dependency>
        <groupId>com.alibaba</groupId>
        <artifactId>fastjson</artifactId>
        <version>1.2.47</version>
    </dependency>
    <!-- 添加CoresFilter过滤器依赖 -->
    <dependency>
    
        <groupId>com.thetransactioncompany</groupId>
        <artifactId>cors-filter</artifactId>
        <version>2.5</version>
    </dependency>
  </dependencies>
  
  
  <build>
     <plugins>
        <!-- 
            tomcat插件，maven内嵌的tomcat 
            作用：用来测试maven的web项目
        -->
        <plugin>
             <groupId>org.apache.tomcat.maven</groupId>
             <artifactId>tomcat7-maven-plugin</artifactId>
             <version>2.2</version>
             <configuration>
                <port>7070</port><!-- tomcat的访问端口 -->
                <path>/server</path><!-- web项目的上下文 -->
                <!-- http://localhost:8080/xxx -->
             </configuration>
        </plugin>
    </plugins>
    
  </build>
  
</project>

三.服务消费方代码(重点)

package com.bjsxt.main;

import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.List;

import org.apache.http.Header;
import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.message.BasicNameValuePair;

import com.alibaba.fastjson.JSON;
import com.bjsxt.pojo.Pet;

public class TestHttpClient {
    public static void main(String[] args) {
        
        try {
            //获取HttpClient链接对象
            HttpClient hc=HttpClients.createDefault();
            //创建URL
            String url="http://localhost:7070/server/pet2";
            //创建请求对象
            HttpPost hp=new HttpPost(url);
            //创建请求实体
                //创建BasicNameValuePair对象，存储键值对请求数据
                BasicNameValuePair bp1=new BasicNameValuePair("pname", "大黄");
                BasicNameValuePair bp2=new BasicNameValuePair("color", "黄色");
                //创建List集合对象，存储请求实体数据
                List<BasicNameValuePair> lb=new ArrayList<>();
                lb.add(bp1);
                lb.add(bp2);
                //创建封装请求实体数据的对象
                UrlEncodedFormEntity     ufo=new  UrlEncodedFormEntity(lb,"UTF-8");
                //设置实体数据到HttpPost请求对象中
                hp.setEntity(ufo);
            //发起请求
                HttpResponse resp = hc.execute(hp);
            //获取响应头
            Header[] allHeaders = resp.getAllHeaders();
            for(Header h:allHeaders){
                System.out.println(h.getName()+":"+h.getValue());
            }
            //获取响应实体
            InputStream is = resp.getEntity().getContent();
            int len=0;
            //将is字节流，转化为字符流
            InputStreamReader reader = new InputStreamReader(is);
            
            char[] buf=new char[1024];          //创建StringBuffer对象
            StringBuffer result = new StringBuffer();
            while((len=reader.read(buf))!=-1){
                result.append(String.valueOf(buf,0,len));
            }
            System.out.println(result);
            List<Pet> parseArray = JSON.parseArray(result.toString(), Pet.class);
            System.out.println(parseArray);
        } catch (Exception e) {
            // TODO: handle exception
        }
    }
}

pom.xml文件

  <dependencies>
    <!-- httpclient客户端工具包 -->
    <dependency>
        <groupId>org.apache.httpcomponents</groupId>
        <version>4.3.5</version>
        <artifactId>httpclient</artifactId>
    </dependency>
    <!-- javabean对象和json串之间转化为工具包 -->
    <dependency>
        <groupId>com.alibaba</groupId>
        <artifactId>fastjson</artifactId>
        <version>1.2.47</version>
    </dependency>
  </dependencies>
  
  
</project>

四.工具类

下面是自己常用的一个对post和get请求封装的HttpClient工具类

package com.ego.commons.utils;

import java.io.IOException;
import java.net.URI;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;

import org.apache.http.NameValuePair;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.client.utils.URIBuilder;
import org.apache.http.entity.ContentType;
import org.apache.http.entity.StringEntity;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.util.EntityUtils;

public class HttpClientUtil {

    public static String doGet(String url, Map<String, String> param) {

        // 创建Httpclient对象
        CloseableHttpClient httpclient = HttpClients.createDefault();

        String resultString = "";
        CloseableHttpResponse response = null;
        try {
            // 创建uri
            URIBuilder builder = new URIBuilder(url);
            if (param != null) {
                for (String key : param.keySet()) {
                    builder.addParameter(key, param.get(key));
                }
            }
            URI uri = builder.build();

            // 创建http GET请求
            HttpGet httpGet = new HttpGet(uri);

            // 执行请求
            response = httpclient.execute(httpGet);
            // 判断返回状态是否为200
            if (response.getStatusLine().getStatusCode() == 200) {
                resultString = EntityUtils.toString(response.getEntity(), "UTF-8");
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                if (response != null) {
                    response.close();
                }
                httpclient.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return resultString;
    }

    public static String doGet(String url) {
        return doGet(url, null);
    }

    public static String doPost(String url, Map<String, String> param) {
        // 创建Httpclient对象
        CloseableHttpClient httpClient = HttpClients.createDefault();
        CloseableHttpResponse response = null;
        String resultString = "";
        try {
            // 创建Http Post请求
            HttpPost httpPost = new HttpPost(url);
            // 创建参数列表
            if (param != null) {
                List<NameValuePair> paramList = new ArrayList<>();
                for (String key : param.keySet()) {
                    paramList.add(new BasicNameValuePair(key, param.get(key)));
                }
                // 模拟表单
                UrlEncodedFormEntity entity = new UrlEncodedFormEntity(paramList,"utf-8");
                httpPost.setEntity(entity);
            }
            // 执行http请求
            response = httpClient.execute(httpPost);
            resultString = EntityUtils.toString(response.getEntity(), "utf-8");
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                response.close();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }

        return resultString;
    }

    public static String doPost(String url) {
        return doPost(url, null);
    }
    
    public static String doPostJson(String url, String json) {
        // 创建Httpclient对象
        CloseableHttpClient httpClient = HttpClients.createDefault();
        CloseableHttpResponse response = null;
        String resultString = "";
        try {
            // 创建Http Post请求
            HttpPost httpPost = new HttpPost(url);
            // 创建请求内容
            StringEntity entity = new StringEntity(json, ContentType.APPLICATION_JSON);
            httpPost.setEntity(entity);
            // 执行http请求
            response = httpClient.execute(httpPost);
            resultString = EntityUtils.toString(response.getEntity(), "utf-8");
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                response.close();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }

        return resultString;
    }
}